detrend function

Detrend Multiple Ring-Width Series Simultaneously

This is a wrapper for detrend.series to detrend many ring-width series at once. UTF-8

detrend(rwl, y.name = names(rwl), make.plot = FALSE,
        method = c("Spline", "ModNegExp", "Mean", "Ar", "Friedman",
                   "ModHugershoff", "AgeDepSpline"),
        nyrs = NULL, f = 0.5, pos.slope = FALSE,
        constrain.nls = c("never", "when.fail", "always"),
        verbose = FALSE, return.info = FALSE,
        wt, span = "cv", bass = 0, difference = FALSE)

Arguments

• rwl: a data.frame with series as columns and years as rows such as that produced by read.rwl

• y.name: a character vector of length(ncol(rwl)) that gives the ID of each series. Defaults to the column names of rwl.

• make.plot: a logical flag. Makes plots of the raw data and detrended data if TRUE. See details below.

• method: a character vector to determine the detrending methods. See details below. Possible values are all subsets of

  c("Spline", "ModNegExp", "Mean", "Ar", "Friedman", "ModHugershoff","AgeDepSpline"). Defaults to using all the available methods.

• nyrs: a number giving the rigidity of the smoothing spline, defaults to 0.67 of series length if nyrs is NULL.

• f: a number between 0 and 1 giving the frequency response or wavelength cutoff. Defaults to 0.5.

• pos.slope: a logical flag. Will allow for a positive slope to be used in method "ModNegExp" and "ModHugershoff". If FALSE the line will be horizontal.

• constrain.nls: a character string which controls the constraints of the "ModNegExp" model and the "ModHugershoff". See detrend.series for further details.

• verbose: logical. Write out details?

• return.info: a logical flag. If TRUE, details about models and data will be added to the return value. See Value .

• wt: a numeric vector of case weights for method "Friedman". The default means equals weights.

• span: a numeric value controlling method "Friedman", or "cv" (default) for automatic choice by cross-validation. See supsmu.

• bass: a numeric value controlling the smoothness of the fitted curve in method "Friedman". See supsmu.

• difference: a logical flag. Compute residuals by substraction if TRUE, otherwise use division.

Details

See detrend.series for details on detrending methods. Setting make.plot = TRUE will cause plots of each series to be produced. These could be saved using Devices if desired.

Returns

If one detrending method is used, a data.frame containing the dimensionless detrended ring widths with column names, row names and dimensions of rwl. If more methods are used, a list with ncol(rwl) elements each containing a data.frame

with the detrended ring widths in each column.

If return.info is TRUE, the return value is a list with four parts:

• series: the main result described above (data.frame or list of data.frames)

• curves: the curve or line used to detrend series. Either a data.frame or a list of data.frames.

• model.info: Information about the models corresponding to each output series. A list with one element for each column of rwl. See detrend.series (Value , model.info ) for a description of the contents.

• data.info: Information about the input series. A list

  with one element for each column of rwl. See detrend.series (Value , data.info ).

Note

This function uses the foreach looping construct with the %dopar% operator. For parallel computing and a potential speedup, a parallel backend must be registered before running the function. If verbose is TRUE, parallel computation is disabled.

Author(s)

Andy Bunn. Improved by Mikko Korpela.

See Also

detrend.series

Examples

library(utils)
data(ca533)
## Detrend using modified exponential decay. Returns a data.frame
ca533.rwi <- detrend(rwl = ca533, method = "ModNegExp")
## Detrend using splines and compute
## residuals via subtraction
ca533.rwi <- detrend(rwl = ca533, method = "Spline",
                     difference = TRUE)

## Detrend using modified Hugershoff curve and return info on the model
## fits. Returns a list with: series, curves, modelinfo and data.info
data(co021)
co021.rwi <- detrend(rwl = co021, method = "ModHugershoff",
                     return.info=TRUE)

## Not run:

library(grDevices)
## Detrend using all methods. Returns a list
ca533.rwi <- detrend(rwl = ca533)
## Save a pdf of all series
fname <- tempfile(fileext=".pdf")
print(fname) # tempfile used for output
pdf(fname)
ca533.rwi <- detrend(rwl = ca533, method = c("Spline", "ModNegExp"),
                     make.plot = TRUE)
dev.off()

unlink(fname) # remove the file
## End(Not run)